Nik Malik posted here on why he thinks a pattern known as "dependency injection" beats out rules engines. I was going to write a long post disagreeing but between Charles Young, who does a great job of responding, and Rajgo over on this blog, I am not sure I have much to add!
When it comes to rules, I believe that management and not execution is the issue for many organizations (such as Sun for instance) and that's the weakness for me in Nik's argument. While "dependency injection" may or may not beat out a rule engine, most of us who are serious about rules use business rules management systems and managing code is just way harder, and less effective, that managing rules.
Sorry for the lack of posts recently, had a deadline.